KIEV, Ukraine -- A deepening civil uprising in Ukraine turned deadly Wednesday, and this embattled capital veered toward chaos, after at least three demonstrators died during clashes with police and the first direct negotiations between President Viktor Yanukovych and opposition leaders yielded only threats and ultimatums.
As Mr. Yanukovych met the three principal opposition leaders at the presidential headquarters Wednesday afternoon, protesters and police battled on a main street near the Dynamo soccer stadium. Flames from burning tires leapt into the air, beneath billows of black smoke, and there were sporadic explosions and gunfire, as the standoff entered its third day.
Two protesters were shot and killed early Wednesday during the violence, the general prosecutor's office said in a statement that promised a full investigation but generally put the blame on protesters, calling them "members of extremist-minded groups." At least 300 were injured.
The circumstances of their deaths were murky, but protesters said police had opened fire on them. A third man died after falling from an archway demonstrators had climbed to hurl rocks and firebombs. There were unconfirmed reports in Ukrainian news media of four other fatalities, including two more by gunfire and two bodies apparently found on Kiev's outskirts.
The worsening violence came as Ukraine marked Unity Day, commemorating unification of the country's eastern and western parts in 1919, and it lent a somber note to what is normally a celebration of national pride.
The intractable conflict erupted in November, when Ukraine was ensnared in a battle for influence between Europe and Russia, and Mr. Yanukovych was assailed by demonstrators for breaking a pledge to sign political and free-trade agreements with the European Union. Since then, all conciliation efforts have failed, and protesters have been repeatedly agitated -- first, by police violence and, more recently, by new legislation severely restricting political dissent.
With both sides dug in, further violence seemed virtually unavoidable, even as other nations seemed unsure of what, if anything, they could do.
The opposition leaders, who represent minority factions in parliament, had initially criticized the violence against police. But after the fruitless meeting with Mr. Yanukovych, they demanded that he offer concessions within 24 hours or they were apparently prepared to join the confrontation.
Standing on a stage in Independence Square, which protesters have occupied since early December, opposition leaders addressed the crowd with a sense of foreboding.
"I will not live in shame," said Arseniy P. Yatsenyuk, Parliament leader of Fatherland, the party of jailed former Prime Minister Yulia V. Tymoshenko. "Tomorrow, we will go forward together," he said. "If there will be a bullet in the forehead, so be it. It will be honest, just and brave action." He added, "Viktor Yanukovych, 24 hours are left. Make a decision."
Vitali Klitschko, a former world champion boxer who leads a party called Ukrainian Democratic Alliance for Reform, also addressed Mr. Yanukovych. "If you won't hear the people, they will do everything to make you hear them," he said, adding: "Tomorrow, if the president won't listen to us, we will go into attack. There is no other way."
Oleg Tyagnibok, leader of the nationalist party Svoboda, whose followers have been among the most aggressive demonstrators, said Mr. Yanukovych did not appear to grasp the situation's gravity. "It is very difficult to negotiate with those who are blind," he said.
The leaders were vague about what would occur in the likely event that Mr. Yanukovych failed to meet their demands. Fighting between protesters and police underscored just how little sway they may hold at this point.